JP2012520443A - Storage container for spent nuclear fuel with improved closure - Google Patents

Abstract

  A container for containment of nuclear waste, a sleeve (2) having a longitudinal axis (X), the first longitudinal end (4) being closed by the bottom and the second longitudinal free The second longitudinal free end (6) is closed tightly by a sleeve which is adapted to load the container into the container (6) and welding means carried out at the height of the welding zone. The container is also provided with a flange portion (12) fixed to the inner surface of the sleeve (2) on the side surface of the second longitudinal free end portion (6). The plug (10) has at least one outer diameter substantially equal to at least one inner diameter of the flange portion (12), and the plug (10) is welded to the flange portion (12). It is made so that Les by the welding zone, the inner surface (2) of the sleeve are offset radially towards the inside of the container.

Description

  The present invention relates to a container for storing nuclear waste, in particular spent nuclear fuel.

  Within the scope of irradiated fuel management, irradiated fuel, after being used in a nuclear reactor, typically undergoes a cooling process in a pool in a building known as a nuclear fuel facility, adjacent to the reactor facility.

  Upon completion of this cooling process, the irradiated fuel can be removed from the pool and then transported to a storage location where it can wait for final discharge and be reprocessed or geologic stockpiling.

  The cooling process in the pool has a limited duration due to the reduced capacity of the cooling pond.

  In this context, it provides for the adjustment of irradiated fuel in a plurality of containers that form a first containment barrier, each container is placed in a container that forms a second containment barrier, and the mechanical performance of the assembly. Secure. This container is intended to transport the container to a temporary storage location for the container. The container is then removed from the container stored in the adapted structure.

  The container includes a cylindrical body having a circular shape in cross section and a bottom welded to one end of the main body.

  After the fuel is placed in the container, a plug is welded onto the free end of the barrel, which ensures a tight closure and further forms gripping means for moving the container.

  The welding of the plug on the body is performed by adding a wire. In addition, in order to ensure welding between the surface of the plug and the body of the container, the welding apparatus must play a specific orientation role, so that a relatively complicated welding apparatus is required. Need to be used.

  Also, the weld must be sufficient to lift the container fitted with the plug.

  Therefore, it is an object of the present invention to provide a container made to contain spent fuel that has improved closure.

  A container that achieves the above object includes a cylindrical trunk having a circular cross-sectional view, a bottom that seals the first longitudinal end of the trunk, and a cover that closes the second longitudinal end of the trunk. The second longitudinal end is provided with a flange projecting from the inner surface of the barrel and is formed to form a support for the cover, the cover comprising: It is made to be welded to the flange portion.

  According to the invention, the fixing of the plug to the body of the plug is achieved not by direct welding to the body of the plug, but by welding to the flange of the plug, the weld zone being radially directed towards the axis of the body. Since the welding zone is easily accessible, the welding apparatus no longer needs to have a complex orientation.

  In other words, in order to make the welding means more accessible to the welding zone, the present invention provides a radial offset of the plug welding zone towards the inside of the vessel to improve weld formation. , Simplify the welding means.

  It is preferable that the inner surface of the flange portion has a stepped shape matching the outer peripheral side surface of the plug. Therefore, the plug is placed on the flange portion, and no additive material for welding is required.

  Preferably, a second plug can be used which mainly forms the container handling means, the first plug forming a hermetic barrier. For this reason, the first plug is disposed at a position lowered to the inside of the trunk with respect to the opening end of the trunk, and the second plug is attached to the trunk so as to cover the first plug.

  The gist of the present invention is mainly a container for confining spent nuclear fuel, a sleeve having a longitudinal axis, the first longitudinal end being closed by the bottom and the second longitudinal free A sleeve, the end of which is adapted to load the container, and a plug, which is adapted to securely close the second longitudinal free end by means of welding performed at the height of the welding zone. The weld zone is radially offset toward the inside of the container relative to the inner surface of the sleeve, and the container is disposed on the side of the second longitudinal free end on the inner surface of the sleeve. And the plug has at least one outer diameter substantially equal to at least one inner diameter of the flange portion, and the plug is disposed on the flange portion. It is made to be contact.

  The flange portion is preferably welded to the inner surface of the sleeve.

  A radial offset can be obtained by means of a flange portion secured to the inner surface of the sleeve on the side surface of the second longitudinal free end, and the plug has at least one inner diameter of the flange portion. At least one outer diameter that is substantially equal and the plug is adapted to be welded to the flange portion.

  Preferably, the flange portion comprises a first portion having a large inner diameter and a second portion having a small inner diameter connected by an annular surface forming a step substantially perpendicular to the longitudinal axis. The plug includes an outer surface that matches the inner surface of the flange portion so that the plug is placed on the stepped portion.

  The container includes an operation means for the container to be distinguished from the plug, and the means is fixed to the sleeve at a height position of the free end in the longitudinal direction of the sleeve, and the flange portion is connected to the sleeve. It is preferable that the sleeve is disposed at a position lowered from the longitudinal free end portion and fixed in the sleeve.

  The operating means is formed by a cover having a gripping member at the center of the cover, for example. The cover preferably has an edge with a thickness approximating the thickness of the longitudinal free end of the sleeve so that the cover can be welded to the sleeve without the addition of wires.

  Preferably, the container according to the present invention may be provided with a pushing means for loading, the pushing means being coupled to the inside of the container.

  When the container is circular in section, the pushing means can be formed by a casing, the length of the casing is substantially equal to the length of the inside of the container, and the shape of the casing in cross section is square. Yes, the length of the diagonal of the square is substantially equal to the inner diameter of the container.

  The casing may also include means for exhausting heat released from the load.

  The heat discharging means includes, for example, a fin extending in a longitudinal direction on at least a part of the outer surface of the casing in the maximum dimension direction.

  The plug preferably includes first and second connectors for draining the container, sweeping air from the inside of the container, and pressurizing the container. A discharge pipe disposed inside the container may be provided, the pipe being for sucking water contained in the container and a first free end disposed at the bottom of the container. And a second end connected to one of the connectors.

  Another aspect of the present invention is a method for loading and closing a container according to the present invention, the step of placing a load inside the container, and the step of placing the plug in the flange portion. And welding the plug to the flange portion without any additive material.

  Also, the method of loading and closing may comprise a later step of placing gripping means at the free end of the sleeve and welding the gripping means to the sleeve.

  The invention will be better understood from the following description and the accompanying drawings.

FIG. 1 is a longitudinal sectional view of an embodiment of a container according to the present invention, and spent fuel is not shown. FIG. 2A is a detailed view of FIG. FIG. 2B is a detailed view of FIG. 2C is an enlarged view of the free end of the container of FIG. FIG. 3A is a perspective view of wedging means that can be placed in a container according to the present invention. FIG. 3B is a perspective view of a wedging means that can be placed in a container according to the present invention. 4 is a cross-sectional view taken along the line AA shown in FIG.

  FIG. 1 shows an embodiment of a container according to the invention, which comprises a cylindrical sleeve 2 made of, for example, stainless steel and having a circular cross-section with an axis X. The sleeve 2 has a first longitudinal end 4 and a second longitudinal end 6. The first end 4 of the sleeve 2 is closed by a plate 8 that forms the bottom of the container. This plate 8 is fixed to the sleeve 2 by welding, for example. The plate 8 and the sleeve 2 may be integrally formed by, for example, flow turning.

    The second longitudinal end 6 forms the mounting end of the container and is made to be tightly closed by the plug 10, which is put in place when the container is loaded.

  According to the present invention, the intermediate flange portion 12 is provided at the height position of the second end portion 6 of the sleeve 2, and the plug 10 is fixed thereto.

  The intermediate flange portion 12 has a ring shape that is fixed to the inner surface of the sleeve 2 at the height position of the second longitudinal end portion 6.

  The flange portion 12 is particularly represented in FIGS. 2A and 2B.

  The flange portion 12 is welded to the inner surface of the sleeve 2.

  Preferably, the flange portion 12 has a stepped inner side surface 14 formed by a first portion having a large inner diameter and a second portion having a small inner diameter, and the first and second portions are in relation to the axis X. Connected by a vertical annular surface 16, oriented towards the outside of the container and made to form a support for the plug.

  The outer peripheral surface of the plug 10 is provided with an outer surface that matches that of the flange portion 12. Accordingly, the outer peripheral surface has a first portion having a large outer diameter and a second portion having a small outer diameter, and the first and second portions are placed on the annular surface 16. They are connected by an annular surface 18 that forms the steps that are made. The diameter of the large outer diameter portion of the plug is substantially equal to the diameter of the large inner diameter portion of the flange portion, and the diameter of the small outer diameter portion of the plug is substantially equal to the diameter of the small inner diameter portion of the flange portion.

  According to the invention, during the closure of the container, the plug 10 is welded to the flange part 12 at a height of contact between the outer contours of the large outer diameter part of the plug 10 and the large inner diameter part of the flange part 12. .

  According to the invention, the welding means 23 used (shown in broken lines in FIG. 2B) is simplified. That is, they do not have to have a complex orientation role to reach the weld zone. Further, welding can be performed without adding an additional material, and the welding method and the welding apparatus can be simplified. The weld is formed by the fusion of the material that makes up the contour of the flange 12 and the material that makes up the contour of the plug 10.

  It should be noted that the flange is welded to the sleeve prior to loading the fuel, which greatly simplifies the welding of the flange to the sleeve.

  The plug 10 provides strict protection and confines spent fuel in a volume V defined by the sleeve 2, base and plug.

  For safety reasons, containers with spent fuel can be loaded in the water in the pool. In this loading method, the volume part (volume V) is filled with water and the water is discharged, so that it is necessary to dry the volume part and the fuel contained therein.

  As can be seen in FIG. 2A, a tube 21 formed to drain water is placed in the container, which is connected to the first suction end that terminates in the bottom of the container and to the plug 10. A second discharge end that terminates toward the end, and is formed to be coupled to a first discharge connector 22 carried by the plug, the connector extending through the plug 10. It is attached to the connector 24. This connector can also help to dry the container. Further, the plug 10 includes a second connector 26 for discharging air during drying of the container and pressurization of the container.

  Finally, when the different steps for closing the container are completed, the first connectors 22, 24 and the second connector 26 measure the humidity inside the container and verify the performance of the container over time.

  In a particularly advantageous manner, the container comprises means 28 for manipulating the container without manipulating the plug 10, as shown in FIGS. 1 and 2B.

  Said means 28 forms a cover fixed to the sleeve, which covers the plug 10 by welding directly onto the sleeve. For this reason, the plug 10 is disposed in a position sufficiently lowered from the free end of the sleeve 2 and is fixed in the sleeve 2, and the longitudinal free end receives the cover 28.

  The main function of the cover 28 is not to seal the container, but to allow operation of the container, for example, by a device suspended on an overhead crane. For this purpose, the cover 28 includes a gripping system 30 that protrudes outward. In the illustrated example, the gripping system 30 is a component protruding from the center of the cover. The gripping system can also be formed in a recess shape.

  In this advantageous example, the sealing function and the operating function can be clearly distinguished. Therefore, the tight fixing of the plug 10 to the sleeve via the flange portion 12 does not have to provide a large mechanical resistance to traction, and the traction while the container is being lifted by the mechanical fixation of the cover 28 to the sleeve 2. Corresponding to the force, the mechanical fixing of the cover 28 is not formed to be tight. This distinction of functions simplifies container manufacturing and monitoring.

  Furthermore, it is understood that the level of containment safety provided by the container is improved and can also be sealed with the fixing of the cover 28 to the sleeve 2.

  It should be noted that fixing the cover by welding to the sleeve does not face the same difficulties as securing the plug 10 to the sleeve because the cover is fixed to the longitudinal free end of the sleeve. However, to simplify the overall method, the cover can be attached to the sleeve in the same way as used for plugs by welding without wires. Thus, as shown in FIG. 2C, the radially outer peripheral surface of the cover is formed by a ring 28.1 having a thickness substantially equal to the thickness of the end of the sleeve, thereby achieving wireless welding. can do. The cover 28 includes an annular step 28.2 that is placed on an annular support surface 29 disposed on the inner surface of the sleeve. Due to the design of the cover, the method of welding the plug to the flange and the method of welding the cover to the sleeve are the same, there is no need to change equipment, and the entire process is fast.

  As a modification, the flange portion is manufactured integrally with the sleeve so that the welding process is not performed.

  Also, as shown in FIGS. 3A and 3B, it is particularly preferred that the container comprises means 32 for substantially holding the charge disposed within the container at the center of the container.

  For example, as shown in the drawing, the pushing means 32 is formed by a casing 33 having a square cross section, and the diagonal dimension of the casing 33 is substantially equal to the inner diameter of the container. The immobilization is secured. The spent fuel is disposed inside the casing 33, and the casing 33 holds the spent nuclear fuel in the lateral direction. The casing has a length substantially the same as the length of the inner volume of the container.

  In a particularly advantageous manner, the casing 33 is provided with cooling fins 34 protruding from its outer surface and facilitating the discharge of heat released from the fuel outside the container.

  In FIG. 3A, the fin 34 extends over the entire length of the casing 33. FIG. 3B shows a modification of the pushing means. The casing 33 is provided with four fins 34 ′ with reduced sizes at each of the two longitudinal ends of the casing 33. It extends over only a limited part of the length of the casing 33. The casing 33 is formed by, for example, four sheets 33a to 33d. Further, the plurality of fins 34 may be distributed over the entire length of the casing 33.

  FIG. 4 shows the casing 33 in the container.

  It will be appreciated that the casing may have a different cross-sectional shape, for example an octagonal cross-sectional shape.

  These pushing means are preferably removable. They are placed in place as needed, especially depending on the function of the shape of the container.

  The container loading and closing process according to the present invention will now be described.

  The container according to the present invention is loaded with spent nuclear fuel.

  Next, the plug 10 is installed at an appropriate position in the flange portion 12.

  Next, the plug and the flange portion are closed and the plug and the flange portion are welded together by welding means (indicated by a broken line in FIG. 2B). According to the present invention, the welding means can be entered substantially parallel to the longitudinal axis X of the container since the welding zone is easily accessible.

  If an operating cover 28 is provided, the cover 28 is taken and welded to the longitudinal free end of the container, for example in the same way.

  The container is then ready for operation.

  According to the invention, the container is made so that it can be tightly closed.

  It will be understood that the container in which the plug also serves as the gripping means does not depart from the scope of the present invention.

2 ... Sleeve 4 ... First longitudinal end 6 ... Second longitudinal end 8 ... Plate 10 ... Plug 12 ... Flange 28 ... Cover 32 ... Pushing means 33 ... casing

Claims (14)

A container for containing spent nuclear fuel,
A sleeve (2) having a longitudinal axis (X), a first longitudinal end (4) closed by a bottom, and a second longitudinal free end (2) designed to be loaded into the container ( 6) a sleeve having
A plug (10) made to securely close the second longitudinal free end (6) by welding means carried out at the height of the welding zone;
With
The weld zone is radially offset toward the inside of the container relative to the inner surface of the sleeve;
The container includes a flange portion (12) protruding from the inner surface of the sleeve (2) on a side surface of the second longitudinal free end portion (6),
The plug (10) has at least one outer diameter substantially equal to at least one inner diameter of the flange portion (12) such that the plug (10) is welded to the flange portion (12). A container that is made.   A container according to claim 1, wherein the flange (12) is welded to the inner surface of the sleeve (2).   The flange portion comprises a first portion having a larger inner diameter and a second portion having a smaller inner diameter connected by an annular surface (16) forming a step substantially perpendicular to the longitudinal axis (X). The plug (10) comprises an outer surface that matches the inner surface of the flange portion (12) so as to place the plug (10) on the stepped portion (16). Container as described in.   The container is provided with an operating means (28) for the container to be distinguished from the plug (10), and the means is provided on the sleeve (2) at a height position of the longitudinal free end (6) of the sleeve (2). Fixed, and the flange (12) is located in a position lowered from the longitudinal free end (6) of the sleeve (2) and secured in the sleeve (2). 3. The container according to 3.   The container according to claim 4, wherein the operating means (28) is formed by a cover having a gripping member in the center of the cover.   6. The cover of claim 5, wherein the cover has an edge with a thickness approximating the thickness of the longitudinal free end of the sleeve so that the cover can be welded to the sleeve without adding wire. container.   A container according to any one of the preceding claims, comprising a pushing means (32) for loading, wherein the pushing means (32) is incorporated inside the container.   The container is circular in cross-section, the pushing means (32) can be formed by a casing (33), the length of the casing being substantially equal to the length of the interior of the container, and The container according to claim 7, wherein a shape of the cross-sectional view is a square, and a length of a diagonal line of the square is substantially equal to an inner diameter of the container.   A container according to claim 8, wherein the casing (33) comprises means (34) for exhausting heat released from the charge.   10. A container according to claim 9, wherein the means for discharging heat (34) comprises fins extending in the longitudinal direction in at least a part of the outer surface of the casing (33) in the direction of the maximum dimension.   The plug includes a first connector (22, 24) and a second connector (26) for draining the container, sweeping air from the inside of the container, and pressurizing the container. The container according to any one of 10.   A discharge pipe disposed inside the container, wherein the pipe is a first free end disposed at the bottom of the container and the connector (22) for sucking water contained in the container; The container of claim 11, having a second end connected to one of the two. A method for loading and closing a container according to any one of claims 1 to 12,
Placing a charge inside the container;
Placing the plug (10) in the flange (12);
Welding the plug (10) to the flange portion (12) without additive material;
A method comprising:   14. A step according to claim 13, comprising the latter step of disposing operating means (28) at the longitudinal free end (6) of the sleeve (2) and welding the operating means to the sleeve (2). Method for loading and closing.

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